The present invention relates to a DC to DC converter that admits power from a wide range of fluctuating industrial level voltages and automatically converts those voltages to a regulated DC voltage that is well below the voltage range of the admitted power.
There is a wide range of industrially available utility supplied line voltages to power electrical equipment, ranging from 208 to 600 VAC, and alternatively 270 to 830 VDC. This powered equipment, while containing some modules that require voltage levels within that input range, also contain modules that require a regulated 48 VDC voltage. Additionally, it may be preferred that electrical equipment modules requiring a voltage of less than 48 VDC, be connected to a regulated 48 VDC output voltage as the source voltage for further conversion.
Conventionally, a DC to DC converter is used to convert alternatively a high valued DC voltage to a lower valued DC voltage, or a low valued DC voltage to a higher valued DC voltage. In order to convert a high valued AC voltage to a differently valued DC voltage, a rectification circuit is imposed between an AC line and a DC to DC converter, so that the AC voltage is first converted to a full wave rectified voltage, and subsequently input to the DC to DC converter, to be output as a lowered or raised DC voltage.
Conventional voltage lowering DC to DC converters operate over a 2:1 input range. Beyond that 2:1 range, they are alternatively unstable or are not able to maintain a regulated output, because of the requirement for extremely rapid witching caused by the combination of a high frequency chopping rate and a low duty cycle. OBJECTS AND SUMMARY OF THE INVENTION
It is accordingly an object of the present invention to provide a DC to DC converter that operates automatically over a variable input range of 4:1, and alternatively produce a near constant voltage.
Another object of the present invention to provide a DC to DC converter that operates automatically over a variable input range that is at least four times as great as the near constant output voltage.
It is still a further object of the present invention to provide a DC to DC converter that operates automatically over a fluctuating input range of at least 230 VDC to 940 VDC, outputs a near constant 48 VDC, and produces at least 100 W of power.
Briefly stated, a DC to DC converter for converting an unregulated DC source that may vary over a range from 230 VC to 940 VDC voltage is converted into a regulated 48 VDC output at a regulated current of approximately 2 amperes. The DC to DC converter has a buck topology and includes a high frequency switch with a variable duty cycle, a regulating filter, a current inner control loop, a voltage outer control loop, a latching switch that provides a load bypass during startup, a logic circuit oscillator that controls the high frequency switch frequency duty cycle as a function of both the inner control loop current and the outer control loop voltage, and a circuit that taps the source voltage for a power input to the logic circuit oscillator during startup. The DC to DC converter thus admits a source voltage range of approximately 4:1 and provides a regulated fixed output that ranges from approximately 30% of the source voltage at the lowest accommodated source voltage to approximately 5% of the source voltage at the highest accommodated source voltage.
According to an embodiment of this invention, a DC to DC converter includes a high frequency switch for defining a chopped output train of voltage pulses, an oscillator circuit that includes a switch driver for controlling the opening and closing of the high frequency switch, a regulation circuit that includes an inductor, for regulating the voltage pulse train, and output current and output voltage control signals for varying the duty cycle of the pulse train. The DC to DC converter of the invention additionally includes a switch for limiting the output voltage during the startup of the DC to DC converter, and a means to supply voltage to the internal circuitry of the DC to DC converter from the input voltage until the high frequency switch has begun to operate.